Various types of conveyor systems are known in the prior art. One important application for conveyor systems is that of conveying plastic and/or wire insulating material, normally in the form of plastic pellets, beads or the like, for processing to be used as insulating wire covering, with the conveyors providing for even distribution of the plastic and/or wire insulating material pellets as the pellets are carried or fed to a processing stage.
Normally the wire insulating material pellets or beads are gravity fed from a top mounted hopper onto a tray which uses vibrational forces to carry the pellets downstream and eventually into an output such as a bin, trough, chute or another hopper. Prior to being fed into the top mounted hopper, various additives such as colorants and UV inhibitors (in either liquid or pellet form) are often used and can be mixed into the pellets, which may introduce ferrous material into the pellets.
The addition of the additive to the pellets along with other materials that may have been picked-up prior to arriving at the top mounted hopper may result in the presence of ferrous materials which are attached to some pellets or contained in the body of some pellets. When used as a wire covering, it is obviously important that the plastic and/or wire insulating materials used to coat the wiring do not contain any ferrous materials. As such there is a need to separate and remove pellets containing ferrous materials from the plastic and/or wire insulating materials before further processing since ferrous metals in the insulation can create an electrical hazard. It is preferred that the separation and removal of ferrous materials and pellets, which contain ferrous material from the plastic and/or wire insulating materials, be accomplished prior to the processing stage of the plastic and/or wire insulating materials such as during conveying plastic and/or wire insulating for processing into electrically insulating wire covering. One of the difficulties with prior art magnetic separators is that it is difficult to completely remove all the articles that contain minute amounts of ferrous materials since the weight of the non-ferrous portion of article or other non-magnetic forces may be such that the magnetic attraction of the ferrous material in the article to the magnet is insufficient to separate the articles containing ferrous materials from the articles that are free of ferrous materials.
There is a need for a magnetic separator that has the ability to separate and remove articles containing minute amount of ferrous materials from those articles containing non-ferrous materials. This is partially true in the manufacture of wire insulation where the material in the articles used for making electrical wire insulation may be in the form of pellets of plastic or other wire insulating material. Typically, the pellets are processed to form an insulating cover for an electrical wire; however, even minute amounts of ferrous materials in the pellets can cause electrical problems. Typically, magnetic separators have not been able to separate articles with minute amounts of ferrous materials from those articles of non-ferrous materials. However, for safety reasons it is important to ensure that articles of ferrous material, article containing ferrous materials are separated from the articles of plastic and/or wire insulating material which are free of non-ferrous material before the articles are further processed.